The presently disclosed subject matter relates to control of uninterruptible power supplies (UPSs).
An uninterruptible power supply (UPS) is an electrical device that can supply power to a load despite variations in quality and/or availability of utility-based power. One common type of UPS is a double-conversion UPS. A double-conversion UPS receives power from a utility power grid, converts the utility power from alternating current (AC) to direct current (DC) in a rectifier, and stores at least some of this power in an energy storage device. An inverter changes the DC power from the rectifier and/or the energy storage device into an AC power waveform. The AC power waveform may be supplied to the load.
Because multiple-conversion operation is inefficient, many UPS devices can operate in an alternative mode to reduce inefficiencies. In a power-saving mode termed “eco-mode,” power to the load is supplied primarily through a bypass from the utility to the load. In this power-saving mode, power is supplied via double-conversion only upon a power supply disturbance from utility. While such a power-saving mode may be more efficient, when such disturbances to the utility power supply occur, they could disrupt power to the load. In many UPS applications, however, even a temporary disruption may be unacceptable.